Many medicament delivery devices are developed for self-administration, i.e. a user performs the medicament delivery by her-, or himself. This requires a medicament delivery device which is reliable, accurate, safe and easy to use. In order to meet these requirements, the risk of human errors must be minimized, the number of actions that need to be performed in order to receive a dose have to be reduced and the device must be intuitive to use. Thus, in order to minimize the risk of human errors, it is desirable to have a device that accurately provides a user with confirmation that he/she has received a complete dose of medicament.
Medicament delivery devices such as injection devices providing automatic or manual delivery member insertion, automatic injection of a medicament, automatic delivery member retraction or automatic covering of the delivery member are known in the art. Although these injection devices have a number of advantages, there is always room for improvement. For example, a device that provides both a complete delivery of medicament and release of a member that produces a reliable audible and/or tactile and/or visible confirmation to the user that the delivery has been completed, has hitherto required extremely tight tolerances in manufacturing.
Such a release of a member for producing a reliable end-of-dose confirmation to the user is disclosed in WO2011043714A1. The releasing action is accomplished by disengaging a holding member from a plunger rod once the plunger rod has terminated its movement for delivering the medicament. The termination of the plunger rod displacement and the disengaging of the plunger rod from the holding member must occur simultaneously if both a complete delivery of a medicament and a release of the holding member which produces the reliable audible and/or tactile and/or visible confirmation to the user that the delivery has been completed are to be accomplished.
Thus, in WO2011043714A1 there is only one mechanical position that is used to activate the release of the second activation member at the point where it is expected that the plunger displacement will terminate. The precision of the timing of the termination of plunger displacement and disengagement of the plunger from the second activation member relies on the manufacturing and assembly dimensions of the parts of the device and thus the tolerances play an important role in the proper functioning of the device.
Document EP 2 705 861 discloses a medicament delivery device comprising a so called controlling means for producing sensory information, e.g. that an injection sequence has been completed. The device is further arranged with so called temporizing means, i.e. a delay mechanism that affects the controlling means such that the generation of the information is delayed, in order to ascertain that a sequence is really completed when the signal is produced such that the device can be removed.
The application of the controlling means as well as of the temporizing means is rather complicated, comprising a rotatable cog wheel having the rotational speed controlled and reduced, e.g. by grease. The cog wheel is operably connected to a sensory indicator via a ratchet rail on the controlling means and temporizing means assembly. The controlling means and temporizing means assembly are in a preloaded state before activation. When the device is used the controlling means and temporizing means assembly are released near the end of the injection sequence. The ratchet will move but the movement is slowed down by the cog wheel co-acting with the grease, thereby delaying the action of the sensory indicator.
As can be understood, there are a large number of components comprised in the solution that need to interact with each other in order to obtain the delayed signal. There is thus room for improvements in the technical area.